Research On The Performance Of Assisted Regeneration And Soot Distribution Features Of Catalyzed Diesel Particulate Filters

In this paper,the optimal asymmetry ratio was researched based on the asymmetrical structure CDPF,and then the optimal asymmetry ratio was applied to study the catalyzed regeneration performance,finally the soot distribution in the channel and wall were analyzed.The results are beneficial to increase the soot capacity,extend the lives of filters and couple with different after-treatment systems.Firstly,the optimal asymmetry ratio was researched by comparing pressure drop under different operation conditions through the validated model.The results show that,the optimal asymmetry ratio is 1.4 under different soot loading.When the exhaust flow is relatively high,the optimal asymmetry ratio is 1.4,and the optimal asymmetry ratio is 1.3 when the flow is relatively low.At 0 g/L soot loading,the optimal asymmetry ratio is 1.4 when temperature lower than 345°C,and change to 1.3 when temperature is over 345°C;at 6 g/L soot loading,the optimal asymmetry ratio is 1.4.The optimal asymmetry ratio is 1.4 under different oxygen concentration.Under different NO2concentration,the optimal asymmetry ratio is 1.3 and 1.4 at 0 g/L and 6 g/L soot loading.Hence,based on this study,the optimal asymmetry ratio is limited in the range of 1.3-1.4 under different operation conditions.Secondly,the passive regeneration performance and NO2/NOx downstream of the CDPF were researched.The deposition speed is equal to oxidation speed when the temperature is around 330°C,which means CDPF reaches balance state.By comparing the regeneration performance under different conditions,inlet temperature is a decisive factor on the regeneration speed,regeneration speed at low or high temperatures do not change with other parameters.At the temperature of 330°C,the values of reaching balance state are that,space velocity is 11.8 s^-1;O2 concentration is 15%;NO2concentration is 60 ppm.Based on this operation load,the range of NO2/NOx ratio is around 0.20 to 0.65.The NO2/NOx ratio reaches its maximum value when the exhaust temperature is about 330°C.The NO2/NOx ratio decreases with increase of space velocity.The NO2/NOx ratio increases with increase of the NO2 and O2 concentration and NO2/NOx,the influence level is that:O2>NO2/PM>NO2.Finally,the soot distribution features and influence parameters were studied.The research results show that:the mass in the filter wall increases steeply and then decreases slowly;soot distribution in the cake layer has a minimum thickness at appropriately 0.30 of the dimensionless channel length,and the edges at the inlet and outlet have the maximum thickness.The exhaust parameters,including temperature,flow,O2 concentration and NO2 concentration,mainly have an effect on the thickness of soot distribution through influencing performance of the NO2 assisted regeneration,the temperature has the largest influence,and the thickness of soot distribution in the cake layer is more sensitive to the concentration of NO2 than O2.The structure parameters,including the ratio of length to diameter,the ratio of inlet diameter to outlet and channel density,have a significant effect on the shape of the soot distribution in cake layer.With the increasing of the structure parameters,the soot distribution tends to be uneven,and the channel density has the largest impact,which would make the position of the lowest point tends to move to the rear end,while the increasing of the ratio of inlet diameter to outlet would make the point move to the front end.